• Journal of Biomedical Engineering Research
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• v.24 no.1
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• pp.37-44
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• 2003

This experimental study is aimed at evaluating the hydrodynamic performance of newly designed self-expandable graft stents under steady flow condition. Two graft stents with different coating materials and a bare TiNi metallic stent for comparison test were used in the experiment. Pressure variation and velocity distribution at the upstream and downstream of the stents were measured at flow rates of 5, 10, and 15 l/min, respectively. Pressure loss due to insertion of the stent increased with increasing flow rate exponentially as expected. At a flow rate of 15 l/min, pressure loss of Polyure-thane(PU)-coated graft stent was 6 times higher than that of TiNi metallic stent, while the pressure loss of a porous Polytetrafluoroethylene(PTFE)-coated graft stent was comparable to a bare TiNi metallic stent. Velocity profiles of the porous PTFE-coated graft stent were similar to those of a bare TiNi metallic stent regardless of flow rate. Furthermore, the velocity profile of PU-coated graft stent revealed an asymmetrical and relatively low central velocity at a higher flow rate than 10 1/min, expecially, where the effects resulted in increases of wall shear stress and normal stress. The worse hydrodynamic behavior of PU-coated graft stent than the other two stents might be attributed to formation of folds due to poor flexibility of coated material when inserting the graft stent into the pipe with a more smaller size, which later gave rise non-symmetry of flow area, increase of surface roughness and jet flow via the crevice between the stent and cylinder wall.

• Progress in Medical Physics
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• v.20 no.3
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• pp.119-124
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• 2009

Stents are frequently used throughout the human body. They keep pathways open in vascular or nonvascular duct for a long time. Therefore its stability is very important factor. In recent years, aconsiderable amount of research has been carried out in order to estimate mechanical properties of the stent such as expansion pressure behavior, radial recoil and longitudinal recoil using FEM (Finite element analyses). However, published works on simulation of stent fatigue behavior using FEM are relatively rare. In this paper, a nonlinear finite-element methodwas employed to analyses the compression of a stent using external pressure and fatigue behavior. Finite element analyses for the stent system were performed using NASTRAN FX. In conclusion this paper shows how the stent is behaved in the body, and its fatigue behavior.

• 순환기질환의공학회:학술대회논문집
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• 2003.11a
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• pp.30-31
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• 2003

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1306-1309
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• 2003

In the present paper, finite element analyses were carried out to evaluate the most important feature of a stent, that is. high radial strength and flexibility. Palmaz-Schatz 154 stent and two new models(stent A, stent B) were selected because they are the most representatives of tubular stents. Finite element analyses for the stent system were performed using ABAQUS/Explicit code. As a result, Palmaz-Schatz 154 stent shows sufficient radial strength but it needs some improvement in general properties such as high flexibility, low elastic recoil, low longitudinal contraction and low metal coverage area. Other two models show that sufficient flexibility, foreshortening and longitudinal recoil.

• Journal of radiological science and technology
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• v.30 no.3
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• pp.205-212
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• 2007

To evaluate the feasibility and efficacy of a pulsatile aortic aneurysm phantoms for in-vitro study. The phantoms consisted of a pulsating motor part(heart part) and an aortic aneurysm part, which mimicked true physiologic conditions. The heart part was created from a high-pressured water pump and a pulsatile flow solenoid valve for the simulation of aortic flow. The aortic aneurysm part was manufactured from paper clay, which was placed inside a acrylic plastic square box, where liquid silicone was poured. After the silicone was formed, the clay was removed, and a silicone tube was used to connect the heart and aneurysm part. We measured the change in pressure as related to the opening time(pulse rate, Kruskal-Wallis method) and pressure before and after the stent-graft implantation(n = 5, Wilcoxon's signed ranks test). The changes in blood pressures according to pulse rate were all statistically significant(p<0.05). The systolic/diastolic pressures at the proximal aorta, the aortic aneurysm, and the distal aorta of the model were $157.80{\pm}1.92/130.20{\pm}1.92$, $159.40{\pm}1.14/134.00{\pm}2.92$, and $147.20{\pm}1.480/129.60{\pm}2.70\;mmHg$, respectively, when the pulse rate was 0.5 beat/second. The pressures changed to $161.40{\pm}1.34/90.20{\pm}1.64$, $175.00{\pm}1.58/93.00{\pm}1.58$, and $176.80{\pm}1.48/90.80{\pm}1.92\;mmHg$, respectively, when the pulse rate was 1.0 beat/second, and $159.40{\pm}1.82/127.20{\pm}1.48$, $166.60{\pm}1.67/138.00{\pm}1.87$, and $161.00{\pm}1.22/135.40{\pm}1.67\;mmHg$, respectively, when it was 1.5 beat/second. When pulse rate was set at 1.0 beat/second, the pressures were $143.60{\pm}1.67/90.20{\pm}1.64$, $147.20{\pm}1.92/84.60{\pm}1.82$, and $137.40{\pm}1.52/88.80{\pm}1.64\;mmHg$ after stent-graft implantation. The changes of pressure before and after stent-graft implantation were statistically significant(p<0.05) except the diastolic pressures at the proximal(p =1.00) and distal aorta(p=0.157). The aortic aneurysm phantoms seems to be useful for the evaluation of the efficacy of stent-graft before animal or clinical studies because of its easy reproducibility and ability to display a wide range of pressures.

• Journal of Veterinary Clinics
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• v.26 no.1
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• pp.48-53
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• 2009

A 4-year-old intact male Shih Tzu dog (5.4 kg of body weight) was referred with primary complaints of heart murmur and exercise intolerance. Diagnostic studies found severe valvular pulmonic stenosis (peak velocity of 6.4 m/s, pressure gradient 165 mmHg). The dog was treated with 3 cm (length) ${\times}$ 1.5 cm (diameter) of Palmaz biliary stent. The outcome of stent placement was favorable and remarkably reduced the severity of PS (6.4 m/s to 3.0 m/s of peak velocity). Clinical condition was remarkably improved with the absence of cardiac murmur, although mild pulmonic regurgitation existed from the day of stent placement. To our best knowledge, this case is the first clinical trial for treating PS with intravascular stent in Korea.

• Korean Journal of Head & Neck Oncology
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• v.30 no.2
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• pp.109-114
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• 2014

갑상선절제술은 내분비 외과의사가 하는 수술 중 가장 안전한 수술이지만 수술 중 기도나 식도가 손상 받을 수 있으므로 각별한 주의를 기울여야 한다. 특히 기도 괴사와 같이 생명에 위협을 주는 합병증이 있음을 유념해야 한다. 본 논문은 갑상선 전 절제술과 승모판 치환술을 함께 받은 72세 여성환자가 수술 후 3일만에 기도 괴사가 발생한 케이스이다. 3개의 기관륜에 걸쳐 괴사가 발생되어 있었다. 괴사된 조직을 제거하고, 이후 지속적인 괴사조직에 대한 제거와 치료와 적으로 기관개창술을 시행하고, 자연폐쇄를 유도하여 성공적으로 치료되었다. 비슷한 여러 논문들을 살펴본 결과 기도 괴사를 유발하는 요인으로는 조절되지 않는 기침, 여성, 갑상샘중독 결절, 기도 삽관 시 발생되는 손상, 삽관튜브 커프의 과팽창으로 기도가 장시간 높은 압력으로 압박되었을 때, 적절하기 않은 커프 크기, 삽관튜브 커프의 공기를 빼지 않고 무리하게 움직였을 때, 출혈이 많을 때, 과도한 전기소작으로 인한 손상, 기도로 가는 혈관손상으로 인한 혈액공급의 차단, 감염 등으로 보고 있다. 치료는 기도의 괴사와 감염의 정도에 따라 달라질 수 있다. 일차 봉합술, 일시적 스토마 형성, 일시적 기관조루술, 단단연결술, 기도 스텐트 설치술, 근육피판 재건술, 보존적 치료 등을 시행할 수 있다. 기도 괴사에 대한 위험인자와 치료에 대해서는 아직 확실히 적립되지 않은 상태이다. 드문 합병증이지만 생명을 위협할 수 있는 이러한 합병증에 대해 항상 염두 해 두고 수술 시 신중을 기하고 문제 발생시 신속한 대응을 해야겠다.